The invention relates to an over voltage protector circuit and, more particularly, to an over voltage protector circuit to prevent alternating voltages commonly supplied by public utilities in excess of a predetermined level. The present invention is a very simple and economic voltage control circuit employing inexpensive components to eliminate alternating voltages in excess of a predetermined amount. Back-to-back transistors in a common base configuration are connected in series with the primary winding of an output transformer. The bias voltages being supplied to the transistors will vary with the alternating current unless the alternating current exceeds a predetermined level, positive or a negative. Once the predetermined level has been reached a zener diode in series with the secondary winding of the output transformer begins to conduct thereby preventing a further increase in the bias voltage of the transistor which, consequently, prevents a further increase in the output voltage.